REBUS creates a sensitive space where the interaction is independent of external light or sound. When REBUS is turned on, an electromagnetic field is transmitted and then received, creating an immaterial interface where invisible affordances can be touched and manipulated with the hands and the body. The sound is modulated by creating interferences between the transmitting and the receiving antenna. REBUS can remind of a Theremin and can be programmed to emulate one, but the compositional possibilities and applications of this instrument are potentially infinite. The question whether the senses can be trained to perceive the electromagnetic field and generate new forms of perception is immanent to the work.